Copperhead /Vintage US820 Engines

[mcbob]

Well fella's being a new kid on the block with US820 i have read a few tid bits that concern me as regards these engines weak points ie: flywheels blowing apart and rod bolt failures.

Would you fellas care to enlighten me more
Have these failings been addressed ..... hope so.

Mc Bob.

[louie figone]

McBob-

The Copperhead engines have the new rod bolts made by ARP for Dave Bonbright, they are rated at 320,000 psi as to the old rod bolts rated at 180,000 psi. The old style rod bolts are fine in an industrial application in the 820. The Copperhead and Vintage 820 are designed for racing applications.
Have not heard of flywheels coming apart, that happened back in the '60's when the 820 was first introduced.

Louie

[Rob Voska]

NOTE SAFETY WARNING
ALL flywheels should be inspected both visually and "ringing" them like a grinding wheels to check for cracks. (hold with a screwdriver in the center hold and tap with a wood hammer handle. Crack will be dull and a good flywheel will ring like a bell) There is no knowing where these parts have been and just because it looks OK does not mean it is OK. Please be safe.

[mcbob]

Thanks fellas anything else a fella should know ?

Mc Bob.

[Rick Chapman]

Bob,
I ran the McCulloch spline head rod bolts in most of my 820's. I never had any rod bolt failure and we ran them on the Enduros. I did replace them every 2 year, just in case...
I did have one flywheel crack when I was tighting onto the crank. It cracked at the keyway slot..
Rick

[ted johnson]

Hi, guys; Rick, I'm putting the 320 KSI Bonbright bolts in my 101! Cheap insurance. You would need to shorten them for the 101; Dave B. can tell you by how much, or you may sweet talk him into shortening them (he's busy as a one-armed paper hanger ). The rod-cap hole MUST be chamfered to clear the under-head fillet on the bolts - I used a 1/4" carbide-tipped masonry bit and chamfered them about .050. I also bought and used a Dremel #83142 cone-pointed silicon carbide grinding stone in the drill-press to finish and smooth the chamfer so as not to provide a place for stress cracks. Still cheap insurance! Ted

[Rick Chapman]

Thanks for the info, Ted....
I usually use the spline head rod bolts but if I want to keep the engine Time Correct, I have some 150,000 tensil strength cap screws. I have never had a Mc Rod bolt brake. In fact I used the cap screws in a number of customers engines with no failure. I have a feeling that guys try and cheapen' it out by not changing something as simple as the rod bolts, and an item that takes a lot of abuse, like they should. So it sounds like the rod bolts are weak or no good. Every engine I sell, or rebuild, I make sure I put new rod bolts in.
Rick

[louie figone]

Rick, I have used the Mc splined rod bolts in my West Bends also, they are rated at 210,000 psi, I never broke a rod bolt in the past but I did change them whenever the engines were taken apart, I think the problem comes from reusing the rod bolts, the new ARP bolts can be reused many times. It's cheap insurance, the only problem is clearance, I use the Mc splined bolts in my Power Products with a West Bend rod, I did not want to grind on the cases, there's not much meat there to begin with.

Louie

[Tom Smith]

McBob, I can't think of any reason why an 820 hot saw shouldn't use a titanium rod except cost. The ancient Carrillo WB-820 steel H-beam rods used hollow dowels and 12x28 UNF twelve point SPS cap screws. It is still a far better looking 820 rod than any of the others I've seen including the new ones. Now days guys are turning 20,000 rpm using titanium rods with stud and nut fasteners instead of the 12 point or torx rod bolts. You need to space the crankcase stuffer out a bit, similar to a Big-J rod or a Horstman stroker crank in an 820. I'm starting to collect the parts to build the first ever NOS 820's I ever owned myself. Thinking about using Mc tungsten counterweights in them. T.

[mcbob]

McBob, I can't think of any reason why an 820 hot saw shouldn't use a titanium rod except cost. The ancient Carrillo WB-820 steel H-beam rods used hollow dowels and 12x28 UNF twelve point SPS cap screws. It is still a far better looking 820 rod than any of the others I've seen including the new ones. Now days guys are turning 20,000 rpm using titanium rods with stud and nut fasteners instead of the 12 point or torx rod bolts. You need to space the crankcase stuffer out a bit, similar to a Big-J rod or a Horstman stroker crank in an 820. I'm starting to collect the parts to build the first ever NOS 820's I ever owned myself. Thinking about using Mc tungsten counterweights in them. T.

Well Tom
I too have a pair of tungsten counterweights which i should have fitted prior to replacing the crank i got the counterweights off Rick when i bought his tapered crank for the Copperhead.

Where's a fella find these titanium rods

Mc Bob.